The word "even" is here because the Sadducees might not have been surprised that some scriptures say that the dead are raised, but they did not expect Moses to have written something like that. Alternate translation: "But even Moses showed that dead people rise from the dead" (See: [[rc://en/ta/man/jit/figs-activepassive]])
The implied information can be supplied. Alternate translation: "in the scripture about the burning bush, where he wrote about the Lord being" (See: [[rc://en/ta/man/jit/figs-explicit]])